Soldering iron tip assembly and cordless soldering iron embodying same

ABSTRACT

An electrically highly efficient soldering iron tip assembly having a heatable tip member, a resistance heating element in effective relation with the member and means including a pair of electrical conductors for supporting the element and member and for energizing the element, the combined operating resistance of the conductors being less than 10% of the operating resistance of the heating element &#39;&#39;&#39;&#39;and having a heat conductance of less than one-half that of copper conductors of the same cross sectional area&#39;&#39;&#39;&#39;, the power consumption of the element in operation and the minimum transverse cross-sectional area of the supporting and energizing means being such that the quotient thereof is more than 4000 watts per square inch. The cordless soldering iron embodying the aforesaid tip assembly has a housing containing rechargeable battery means, a switch, a pair of terminals and electrical conductors connecting same in circuit. Optionally, the soldering iron is provided with a lamp to illuminate the work and indicate the charge condition of the battery means, and, if desired, a signal means visible on the top of the housing to indicate switch position and charge condition of the battery means.

United States Patent 1 Walton I Aug. 12, 1975 [75] Inventor: William M. Walton, Sterling, Ill.

[73] Assignee: Wahl Clipper Corporation, Sterling,

Ill.

22 Filed: Sept. 26, 1973 21 Appl. No.: 401,060

Related US. Application Data [63] Continuation of Ser. No. 214,303, Dec. 30, 1971,

abandoned.

[52] US. Cl. 219/229; 219/230; 219/237; 219/240; 219/268; 219/506; 219/533; 228/51 [51] Int. Cl. H051) 3/02; B23k 3/04 [58] Field of Search 219/221, 227-242,

FOREIGN PATENTS OR APPLICATIONS 3/1970 United Kingdom 219/240 10/1933 Germany ..2l9/233 6/1944 France ..219/238 Primary Examiner-A. Bartis Attorney, Agent, or Firm-Edward U. Dithmar [5 7] ABSTRACT An electrically highly efficient soldering iron tip assembly having a heatable tip member, a resistance heating element in effective relation with the member and means including a pair of electrical conductors for supporting the element and member and for energizing the element, the combined operating resistance of the conductors being less than 10% of the operating resistance of the heating element and having a heat conductance of less than one-half that of copper conductors of the same cross sectional area, the power consumption of the element in operation and the minimum transverse cross-sectional area of the supporting and energizing means being such that the quotient thereof is more than 4000 watts per square inch. The

I cordless soldering iron embodying the aforesaid tip assembly has a housing containing rechargeable battery means, a switch, a pair of terminals and electrical conductors connecting same in circuit. Optionally, the soldering iron is provided with a lamp to illuminate the work and indicate the charge condition of the battery means, and, if desired, a signal means visible on the top of the housing to indicate switch position and charge condition of the battery means.

8 Claims, 7 Drawing Figures SOLDERING IRON TIP ASSEMBLY AND CORDLESS SOLDERING IRON EMBODYING I SAL IE I This application is a continuation of prior application Ser. No. 214,303, filed Dec. 30, 1-971 now abandoned.

BACKGROUND or THE INVENTION This invention relates to an electrically highly efficient tip assembly for a soldering iron and a cordless soldering iron embodying the tip assembly.

More particularly, the tip assembly. of the invention employs a resistance heating element and is designed so that most of the generated heat is available at the soldering tip for transfer to the work, and no significant amount of heat is conducted away from the tip through the means provided to support the tip and to conduct current to the heating element. I

As far as the applicant knows, prior sq iering iron tip assemblies are grossly inefficient electrically clue in large part to high heat conduction away from the soldering tip through the means used to support the tip and to energize the heating element. Such assemblies are unsatisfactory in a cordless soldering iron for obvious reasons, and in soldering irons of thecord type that require a costly transformer which also is inefficient electrically. I

The closest prior art presently known to applicant is set forth in US. Pat. Nos. 2,973,422 and 3,141,087. US. Pat. No. 3,141,956 in pertinent respects is substantially the same as Pat. No. 3,141,087.

SUMMARY OF THE INVENTION The invention resides in an electrically highly efficient soldering iron tip assembly which includes a heatable tip member, a heating element of resistance material in effective relation with the member and means including a pair of electrical conductors extending from the ends of the element. for supporting the element and member and for energizing the element. The combined resistance of the conductors in the supporting and energizing means when the tip assembly is in operation and thus at elevated temperature is less than of the operating resistance of the heating element.

The heating element in the tip assembly has a predetermined power consumption in operation at elevated temperature, for example, watts in one embodiment of the invention. Further, the aforesaid supportingand energizing means, whether it be only the pair of electrical conductors, or electrical conductors and an additional support element, has a minimum transverse cross-sectional area. In accordance with the invention, the quotient of the predetermined power consumption in watts and the minimum transverse cross-sectional area is greater than 4000 watts per square inch. This relationship defines a tip assembly wherein the supporting and energizing means provide requisite support and electrical conductivity, and have a sufficiently small minimum cross-sectional area to prevent significant heat transfer to the body of the soldering iron on which the tip assembly is mounted, rendering the tip assembly electrically highly efficient.

Other aspects of the invention deal with additional details of the tip assembly and, in addition, a cordless soldering iron embodying the tip assembly, including a housing, terminal structure on the housing for mounting the tip assembly, a lamp for illuminating the-soldering tip and indicating the charge condition of a self- BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevational view, partly broken away, of a cordlesssoldering iron embodying the invention.

FIG. 2 is a front elevational view of the cordless soldering iron shown in FIG. 1.

FIG. 3 is a rear elevational view thereof.

FIG. 4 is a top plan view of the cordless soldering iron of FIG. 1, the upper housing portion being removed to expose the components within the housing.

FIG. 5 is a fragmentary bottom view of the cordless solderingiron of FIG. 1 showing details of the invention.

FIG. 6 is an enlarged view of the tip assembly of the invention. 2

FIG. 7 is a sectional view through the tip assembly on line 77 of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1-3 of the drawing, a cordless soldering iron 10, which will be described first, includes an elongated housing 11 of insulating material having lower housing portion 12 and upper housing portion 13.

As shown, upper housing portion 13 tapers at its forward end toward the housing axis as shown at 15, both horizontally and vertically. Lower housing portion 12 at its forward end also tapers horizontally toward the housing axis as shown at 16 in FIG. 4, and in the forward region at the bottom is provided with a recess as shown at 17 in FIG. 1.

Still referring to FIG. 1, rear wall 18 of recess 17 inclines rearwardly and terminates at its lower end in a transverse straight foot 19, also shown in FIGS. 2, 3 and 5, which imparts stability when the soldering iron is chargeable from dead" to full charge in about twelve hours at a safe charging rate. Rear terminal 26 of battery means 25 is connected by conductor 27 to external terminal 28 which, together with adjacent external terminal 29, constitute connections for an associated battery charger (not shown). External terminal 29 is connected by conductor 30 to stationary switch element 31 which in turn is connected to front terminal 32 of battery means 25.

Still referring to FIG. 4, a pair of spaced terminals 35 and 36 are mounted in recesses provided in the forward end of lower housing portion 12. Terminal 35, as shown, has connected thereto a spring strip 37 (shown broken away) which is secured for stability to a boss projecting from the bottom of housing portion 12 by a screw 38. The free end 40 of spring strip 37 constitutes a movable switch element which normally is spaced from previously mentioned stationary switch element 31. Push button 20 is in effective relation with free end 40 of spring strip 37, so that when button 20 is depressed the switch closes, and when released the switch opens. A

Companion forward terminal 36, as shown, is received loosely in a cooperating recess in lower housing portion 12, and is held in place by upper housing portion 13 when the two housing portions are in assembled relation. A conductor 42 connects terminal 36 to rear terminal 26 of battery means 25. Thus, when switch elements 31 and 40 are closed, terminals 35 and 36 are in circuit with battery means 25.

The illustrated embodiment of the invention includes a lamp 45 (FIGS. 1, 2 and mounted in rear wall 18 of recess 17 and directed forwardly of housing 11. As will be seen, lamp 45 directs a beam of light to work being acted upon by the soldering tip presently to be described. Lamp 45 is received in metallic lamp socket 46 (FIG. 4) which is connected electrically to spring strip 37 by conductor 47 secured by screw 38 in contacting relation with the socket. A conductor 49 extends between conductor 42 and the insulated rear end of socket 46 which engages the central terminal of lamp 45. Thus, lamp 45 is connected in shunt with'forward terminals 35 and 36 in circuit with switch elements 31 and 40.

Lamp 45 normally is located on the under side of the soldering iron during use, and the off-on condition thereof may not be observable by the operator, particularly under daylight conditions. In order that the operator readily may be informed as to the off-on condition of the lamp, an indicator or signal is provided on the top of the soldering iron forwardly of push button 20. This indicator includes aligned apertures 50 (FIG. 1) and 51 (FIGS. 4 and 5) in the upper and lower housing portions 13 and 12, respectively, and an elongated light transmitting member 53 (FIG. 1) terminating at its ends in the apertures. Lower aperture 51 is adjacent lamp 45, whereby light from the lamp is transmitted to upper aperture 50 where it is readily visible to the operator. The luminous intensity of lamp 45 and hence the I intensity of the signal in upper aperture 50 are functions of the charge condition of the battery means, and, accordingly, the lamp and indicator tell the operator at least in a general way whether or not the battery means requires recharging, as well as the off-on condition.

A tip assembly generally designated 55 is secured, preferably in detachable manner, to forward terminals 35 and 36. Tip assembly 55 is best shown in enlarged FIGS. 6 and 7.

Referring to FIG. 7, tip assembly 55 comprises an elongated heatable metallic member 56. As shown, member 56 is hollow and closed at its free end 57 which is tapered both laterally and vertically to provide a soldering tip 58 of convenient size and shape. Alternatively, tip 58 may be part of a separate member having telescoping relation with member 56.

A heating element 60, preferably a coil, of resistance material is positioned within member 56 and electrically insulated therefrom by means such as material 61 to the extent necessary to prevent a short circuit across the element. Insulating material 61, if used, has high heat conductivity, and it has been found that ceramic potting material is especially satisfactory.

60 and terminal 35 and 36, and one or both of them 4 serve as the sole support for element 60 and associated member 56. As shown, the forward ends of terminals 35 and 36 contain openings of suitable size to receive the free ends of conductors 62 and 63, and set screws 65 and 66 (FIGS. 4 and 5) are provided to secure the conductors in the terminals in detachable manner.

While it is preferred that one or both of the electrical conductors 62 and 63 provide the sole support for heating element 60 and associated tip member 56, as illustrated, the invention contemplates that another part (not shown) may be used to perform some or all of the supporting function. Such part may or may not be of electrically conducting material. Thus, in broadest aspect, the tip assembly invention contemplates means, including a pair of electrical conducts, for supporting the heating element and member from, and in spaced relation with, the housing and for energizing the element. This supporting and energizing means, of course, has a transverse cross-sectional area.

The aforesaid transverse cross-sectional area in some instances may vary along the length of the supporting and energizing means, as would be the case, for example, with a tubular member (not shown) having one or more circumferential grooves used either as a separate support part of as one of the conductors. When a variation in cross-sectional area exists, the cross-sectional area critical to the invention is the minimum crosssectional area because minimum area mainly controls the amount of heat conducted through the supporting and energizing means to the housing. Such heat, of course, is unavailable for soldering, and thus is a loss resulting in electrical inefficiency.

It has been found that the electrically highly effi- I ciency characteristic of the present tip assembly is due in most part to the comparative values of the power consumption of the heating element in operation (watts) and the aforesaid minimum transverse crosssectional area of the supporting and energizing means (square inches), the values being such that the quotient thereof is more than 4000 watts per square inch. Tip assemblies wherein the comparable quotient is appreciably less than 4000 watts are inefficient and unsatisfactory for use in cordless soldering irons, and, if used in soldering irons of the cord type, usually require a costly transformer.

Tip assemblies wherein the quotient mentioned above is more than 4000 watts per square inch are electrically highly efficient due mainly to the fact that there is no significant heat transfer away from the soldering tip to the body of the soldering iron through the supporting and energizing means extending between the body and the tip member. The provision that the combined operating resistance of the pair of electrical conductors is less than 10% of the operating resistance of the heating element insures the delivery of requisite power to the element and establishes a practical upper limitfor the watts per square inch quotient. As mentioned, 4000 watts per square inch consititutes the lower limit.

Particularly satisfactory results have been obtained with electrical conductors 62 and 63 formed of spring wire of diameter in the range of 0.035 to 0.040 inch,

with the length of the conductors such that they space member 56 about 0.6 inch from the housing.

It further has been found that at least one of the electrical conductors 62 and 63 should be formed of material that has a heat conductance of less than one-half that of copper.

As shown, conductors 62 and 63 as well as the entire tip assembly 55 preferably extend at a small angle to the axis of housing 11. This geometrical relationship places soldering tip 58 in the beam from lamp 45, insuring simultaneous illumination of the tip and the critical portion of the work. Also, this angulation of the tip assembly contributes greatly to ease of operation.

The exterior of member 56 of tip assembly 55, except in the immediate vicinity of soldering tip 58, may be coated with electrical and thermal insulating material (not shown) for the purpose of minimizing heat loss by radiation and conduction, and minimizing short circuits in the work. The latter is a safety factor particularly when using the soldering iron on printed circuit boards and the like.

The illustrated cordless soldering iron embodying the invention is less than 8 inches long, including tip assembly, and weighs less than 6 ounces. It is designed for good feel and balance, factors tending to eliminate fatigue during extended usage. The soldering tip reaches soldering temperature in about 5 seconds, and the iron is capable of soldering up to 60 joints per charge depending on joint size.

From the above description it is thought that the construction and advantages of this invention will be readily apparent to those skilled in the art. Various changes in detail may be made without departing from the spirit or losing the advantages of the invention.

Having thus described the invention, what is claimed as new and desired to secure by Letters Patent is:

1. An electrically and thermally highly efficient cordless soldering iron, comprising:

a housing having a forward end;

a rechargeable battery means of limited capacity in said housing; pair of terminals electrically insulated from each other mounted at the forward end of said housing and connected to said battery means; switch in said housing in circuit with said battery means and said terminals;

a hollow heatable tip member adapted to be supported in spaced relation with the forward end of said housing;

heating element of resistance wire within said tip member in effective heating relation therewith and electrically insulated therefrom, said element having predetermined power consumption in operation; and

pair of electrical conductors of deformable solid wire connected between said heating element and said terminals for energizing said element and for solely supporting said element and said tip member in spaced relation to the forward end of said housing, the combined operating resistance of said conductors being less than 10% of the operating resistance of said element and the heat conductance of said conductors being less than /2 that of copper conductors of the same cross sectional area;

said predetermined power consumption of said element in operation (watts) and the transverse cross sectional area of said electrical conductors (square inches) being such that the quotient thereof is more than 4000 watts per square inch;

said rechargeable battery means having current and voltage ratings sufficient to satisfy said power consumption requirement;

whereby said deformable solid electrical conductors provide requisite support and electrical conductivity with a sufficiently small cross-sectional area to prevent significant heat transfer to said terminals and said housing and to prevent significant heat loss by radiation and conduction from said electrical conductors, rendering said soldering iron electrically and thermally highly efficient.

2. The soldering iron of claim 1 wherein said housing adjacent said terminals has a recess, and with the addition of a lamp connected in circuit with said switch mounted in a wall of said recess to direct light to the work and to indicate the charge condition of said battery means, said lamp positioned so the light beam therefrom is directed to said tip member.

3. The soldering iron of claim 2 wherein said housing has aligned apertures in its top and bottom walls in alignment with said lamp, and with the addition of an elongated light transmitting member terminating in said apertures, the bottom wall aperture adjacent said lamp whereby light from the lamp traverses said light transmittingmember and is visible as a signal in the top wall aperture indicating switch position and charge condition of said battery means.

4. The soldering iron of claim 1 wherein said battery means provides about 2.4 volts and the power consumption of said heating element in operation is about 20 watts.

5. The soldering iron of claim 1 wherein said electrical conductors are spring wire of diameter in the range of 0.035 to 0.040 inches.

6. The soldering iron of claim 1 with the addition of a pair of charging terminals electrically insulated from each other mounted in said housing for connection to an external battery charger, and conductors in said housing connecting said charging terminals to said battery means.

7. The soldering iron of claim 1 wherein said housing is elongated and has two portions meeting on longitudinally extending junction lines, the forward ends of said portions having internal terminal-engaging walls, at least one of said terminals secured solely by said terminal-engaging walls when said housing portions are in assembled relation, said battery means being mounted in a rearward section of said housing.

8. The soldering iron of claim 7 wherein a terminalengaging wall is disposed between said pair of terminals to space said terminals from each other. 

1. An electrically and thermally highly efficient cordless soldering iron, comprising: a housing having a forward end; a rechargeable battery means of limited capacity in said housing; a pair of terminals electrically insulated from each other mounted at the forward end of said housing and connected to said battery means; a switch in said housing in circuit with said battery means and said terminals; a hollow heatable tip member adapted to be supported in spaced relation with the forward end of said housing; a heating element of resistance wire within said tip member in effective heating relation therewith and electrically insulated therefrom, said element having predetermined power consumption in operation; and a pair of electrical conductors of deformable solid wire connected between said heating element and said terminals for energizing said element and for solely supporting said element and said tip member in spaced relation to the forward end of said housing, the combined operating resistance of said conductors being less than 10% of the operating resistance of said element and the heat conductance of said conductors being less than 1/2 that of copper conductors of the same cross sectional area; said predetermined power consumption of said element in operation (watts) and the transverse cross sectional area of said electrical conductors (square inches) being such that the quotient thereof is more than 4000 watts per square inch; said rechargeable battery means having current and voltage ratings sufficient to satisfy said power consumption requirement; whereby said deformable solid electrical conductors provide requisite support and electrical conductivity with a sufficiently small cross-sectional area to prevent significant heat transfer to said terminals and said housing and to prevent significant heat loss by radiation and conduction from said electrical conductors, rendering said soldering iron electrically and thermally highly efficient.
 2. The soldering iron of claim 1 wherein said housing adjacent said terminals has a recess, and with the addition of a lamp connected in circuit with said switch mounted in a wall of said recess to direct light to the work and to indicate the charge condition of said battery means, said lamp positioned so the light beam therefrom is directed to said tip member.
 3. The soldering iron of claim 2 wherein said housing has aligned apertures in its top and bottom walls in alignment with said lamp, and with the addition of an elongated light transmitting member terminating in said apertures, the bottom wall aperture adjacent said lamp whereby light from the lamp traverses said lighT transmitting member and is visible as a signal in the top wall aperture indicating switch position and charge condition of said battery means.
 4. The soldering iron of claim 1 wherein said battery means provides about 2.4 volts and the power consumption of said heating element in operation is about 20 watts.
 5. The soldering iron of claim 1 wherein said electrical conductors are spring wire of diameter in the range of 0.035 to 0.040 inches.
 6. The soldering iron of claim 1 with the addition of a pair of charging terminals electrically insulated from each other mounted in said housing for connection to an external battery charger, and conductors in said housing connecting said charging terminals to said battery means.
 7. The soldering iron of claim 1 wherein said housing is elongated and has two portions meeting on longitudinally extending junction lines, the forward ends of said portions having internal terminal-engaging walls, at least one of said terminals secured solely by said terminal-engaging walls when said housing portions are in assembled relation, said battery means being mounted in a rearward section of said housing.
 8. The soldering iron of claim 7 wherein a terminal-engaging wall is disposed between said pair of terminals to space said terminals from each other. 